In fires of subway stations, the most immediate threat to passeng’e rlsife is not the
direct exposure to fire, but the smoke inhalation because it contains hot air and toxic
gases. To understand the mechanisms driving the motion of smoke is therefore an
important issue of fire safety, and the stack effect is found to be an important
mechanism having significant influence. In this paper,p utwee thceo m
three-dimensional smoke flow fields under various fires happened in a representative
subway station of Taipei Rapid Transit System. To clarify the mechanisms
corresponding to the stack effect, a simplified three-dimensional configuration is also
considered. Results indicate that, without mechanical smoke control, the stack effect
plays a decisive role and is virtually the sole factor influencing the smoke movement.
Because of the stack effect, most or sometimes all of the smoke will choose a vertical
shaft (usually a stairwell) to evacuate, and the cross sectional area of the shaft and the
location of fire determine which shaft is chosen. Present computational results show
the evidences of the importance of the stack effect and provide both valuable
information to the design of the passenger evacuation routes in fires as well as criteria
to the design of smoke control systems of subway stations.
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